1216637856 has 216 divisors, whose sum is σ = 4083268644. Its totient is φ = 342558720.

The previous prime is 1216637837. The next prime is 1216637857. The reversal of 1216637856 is 6587366121.

1216637856 is a `hidden beast` number, since 1 + 2 + 1 + 6 + 637 + 8 + 5 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1123322256 + 93315600 = 33516^2 + 9660^2 .

It is not an unprimeable number, because it can be changed into a prime (1216637857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1029586 + ... + 1030766.

Almost surely, 2^1216637856 is an apocalyptic number.

1216637856 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1216637856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2041634322).

1216637856 is an abundant number, since it is smaller than the sum of its proper divisors (2866630788).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1216637856 is a wasteful number, since it uses less digits than its factorization.

1216637856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1284 (or 1266 counting only the distinct ones).

The product of its digits is 362880, while the sum is 45.

The square root of 1216637856 is about 34880.3362369115. The cubic root of 1216637856 is about 1067.5472558136.

The spelling of 1216637856 in words is "one billion, two hundred sixteen million, six hundred thirty-seven thousand, eight hundred fifty-six".